1. Technical Field
The present invention relates to a process for preparing high purity corosolic acid and high purity ursolic acid.
2. Background Art
Corosolic acid is known to have insulin-like activity (Chem. Pharm. Bull. (1993) 41(12): 2129-2131), to help sugar uptake into cells (Chem. Pharm. Bull. (1993) 41(12): 2129-2131), to have an effect of suppressing elevation of blood glucose level (Planta Med. (1991) 57: 414-416), and the like. Ursolic acid is known to prevent generation of wrinkles (Japanese Patent Laid-open Publication No. H09-143050), to improve fascicular degradation due to ultraviolet rays (Japanese Patent Laid-open Publication No. 2002-255781), to have an antitumor effect (World J Gastroenterol (2002) 8(3): 493-495, World J Gastroenterol (2006) 12(6): 874-879), and the like. Since corosolic acid and ursolic acid have been confirmed to have various effects, respectively, as described above, manufacturing of high purity corosolic acid and high purity ursolic acid has been desired.
As for corosolic acid, a production method of extracting Banaba leaves with hydrous ethanol, treating the extract with activated carbon, then concentrating the extract, and collecting the precipitates (Japanese Patent Laid-open Publication No. 2005-263650); a method of preparing an extract containing corosolic acid from loquat leaves (U.S. Pat. No. 6,908,632), and the like have been disclosed. As for ursolic acid, a method of obtaining a mixed concentrate of ursolic acid and an oleanolic acid derivative (Japanese Patent Laid-open Publication No. 2002-345434), and the like have been disclosed.
Japanese loquat (Scientific name: Eriobotrya japonica; English name: Japanese loquat, Japanese medlar, Japanese plum, Japanese name: Biwa) is an evergreen low fruit tree with a height of 3 to 8 m, and widely distributed in China and Japan. The leaves are oblong with a length of 15 to 30 cm and a width of 3 to 7 cm, and are thick and hard. The leaves are glossy dark green and alternate. In China, the leaves are used for antimicrobial, antitussive, expectorant, diuretic purposes and the alleviation of heat exhaustion. Also, a compress containing infusion of the leaves is used for the alleviation of skin diseases. The leaves are known to contain several triterpene compounds including ursolic acid, oleanolic acid, corosolic acid, and maslic acid (U.S. Patent Application Publication No. 2005/0137259).
However, a process for preparing high purity corosolic acid and high purity ursolic acid using Japanese loquat leaves as a raw material which can be conducted efficiently and under such conditions that corosolic acid and high purity ursolic acid are useful as foods has not been disclosed.